Friday, April 19, 2013

Even the Poster Child Has Problems: Drugs for Hypertension

A perennial theme in this blog is the way American medicine and the general public have been oversold on drug treatment generally, and "prevention" in particular. Prevention is important because the numbers needed to treat, when you are trying to prevent later disease in a population that now has no symptoms, tend to be very high--you may for example need to treat hundreds of people for several years with a drug in order to prevent one death or heart attack or stroke. The possibility that many of those hundreds of people will suffer harm from the drugs, while only one benefits, has to be kept in mind.

A couple of fairly recent studies drive home this point on what many would consider the poster child for successful prevention--drug therapy for high blood pressure. (Subscriptions may be required for articles cited.)

An international team led by Diana Diao did a review for the very respectable Cochrane Collaboration of drug treatment for mild hypertension. Many of us need to be reminded that "mild" hypertension includes people with blood pressure as high as 159/99. In days when practice guidelines and pay-for-performance schedules make doctors feel like criminals for every patient who is not below 140/90, this is worth stating.

Dr. Diao and colleagues identified 4 randomized trials that were good enough to include in their review, including a total of nearly 9000 subjects. They could not find any evidence that drug treatment for hypertension in this range reduced total death rate, strokes, heart attacks, or other cardiovascular events, at least over a 4-5 year period of study. About 9% of all subjects had to be discontinued due to adverse drug reactions.

Now, if you have questions about the value of treating high blood pressure in regular folks, you should neverthess be convinced that it's extremely important in people with diabetes. The main treatment effect seen in successful trials of diabetes treatment (focusing now on the more common adult or Type 2 diabetes, and not speaking of Type 1 or juvenile diabletes that requires insulin) is the result of aggressive treatment of cardiac and vessel risk factors, of which high blood pressure is a major one. Generally it is thought that while you need to try to get blood pressure below 140 for non-diabetics, you need to shoot for 130 in diabetic patients.

So a Canadian group led by Dr. Kerry McBrien did another meta-analysis of randomized trials comparing standard vs. intensive treatment of blood pressure in diabetes-- trying to get blood pressure below 130 (intensive) as opposed to shooting for 140-160 (standard). They found 5 pertinent studies. Across these 5 studies they found no evidence for reduction in total death rate or heart attack in the more-intensive-treatment group. They did however find a slight decrease in the stroke risk--about a 1 percent decreased risk. They also found a lot more adverse drug reactions in the intensive-treatment group, including many that could have been fatal or that required hospitalization.

So what does all this mean? If we take people whose blood pressure is as high as 159/99, there's no good evidence that treating their blood pressure with drugs improves their long-term outcomes. Even in diabetics, the group who most needs good blood pressure control, working to get blood pressure super-low instead of just reasonably low provides hardly any added benefit, but imposes considerable added risk of harm.

So just how did we get brainwashed into thinking that it's medical negligence to allow a patient to go around with a blood pressure of 141/91--and that if need be, put that patient on 3 or 4 different drugs to control this terrible condition? Is it possible that drug industry marketing had anything to do with that? And if this is so for the poster child of successful prevention, hypertension, what does it say about so many other "preventive" regimens that rely on drug treatment?

Hat tip to Primary Care Medical Abstracts, as so often, for the citations.